CN110987247B - Test method for measuring uniform and non-uniform restraining force of concrete-filled steel tubular column by adopting piezoelectric film - Google Patents
Test method for measuring uniform and non-uniform restraining force of concrete-filled steel tubular column by adopting piezoelectric film Download PDFInfo
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- CN110987247B CN110987247B CN201910999442.4A CN201910999442A CN110987247B CN 110987247 B CN110987247 B CN 110987247B CN 201910999442 A CN201910999442 A CN 201910999442A CN 110987247 B CN110987247 B CN 110987247B
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 44
- 239000010959 steel Substances 0.000 title claims abstract description 44
- 239000004567 concrete Substances 0.000 title claims abstract description 40
- 230000000452 restraining effect Effects 0.000 title claims abstract description 21
- 238000010998 test method Methods 0.000 title claims abstract description 7
- 238000000034 method Methods 0.000 claims abstract description 13
- 230000008859 change Effects 0.000 claims abstract description 12
- 230000008569 process Effects 0.000 claims abstract description 10
- 230000000694 effects Effects 0.000 claims description 5
- 238000012669 compression test Methods 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 3
- 230000010287 polarization Effects 0.000 claims description 2
- 238000005259 measurement Methods 0.000 abstract description 4
- 230000035945 sensitivity Effects 0.000 abstract description 4
- 238000010276 construction Methods 0.000 abstract description 2
- 230000036541 health Effects 0.000 abstract description 2
- 230000003993 interaction Effects 0.000 abstract description 2
- 238000012544 monitoring process Methods 0.000 abstract description 2
- 238000011897 real-time detection Methods 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 abstract description 2
- 230000000007 visual effect Effects 0.000 abstract description 2
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 abstract 1
- 239000010408 film Substances 0.000 description 40
- 238000001514 detection method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000009659 non-destructive testing Methods 0.000 description 1
- 239000011376 self-consolidating concrete Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/16—Measuring force or stress, in general using properties of piezoelectric devices
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/30—Columns; Pillars; Struts
- E04C3/34—Columns; Pillars; Struts of concrete other stone-like material, with or without permanent form elements, with or without internal or external reinforcement, e.g. metal coverings
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
- G01N3/06—Special adaptations of indicating or recording means
- G01N3/066—Special adaptations of indicating or recording means with electrical indicating or recording means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/026—Specifications of the specimen
- G01N2203/0262—Shape of the specimen
- G01N2203/0266—Cylindrical specimens
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0676—Force, weight, load, energy, speed or acceleration
Abstract
The invention discloses a test method for measuring uniform and non-uniform restraining force of a concrete filled steel tubular column by adopting a piezoelectric film. The invention pastes the piezoelectric film with the thickness of only 28 mu m on the inner side of the steel pipe, and the hole is opened at the position 2 d-30 d away from the veneering position to lead out a lead wire to output a piezoelectric signal, wherein d is the diameter of the hole, so as to avoid inaccurate measurement of the constraint force at the measuring position caused by stress concentration at the hole opening position. The high sensitivity of the piezoelectric film to dynamic stress is utilized, and the interaction force between the steel pipe and the concrete is measured through the change of electric signals between the upper electrode and the lower electrode of the film. The device of the invention can not damage the interface characteristics of the steel pipe and the concrete, the film is thin and easy to place, the testing device is simple, the measuring operation is easy, the measuring result is visual, the sensitivity and the accuracy are high, the actual measurement of the hoop restraining force in the whole stress process can be realized, the real-time detection of the hoop restraining force in the construction or service process can be realized, and the real-time monitoring of the safety and the health of the structure can be realized.
Description
Technical Field
The invention relates to the technical field of ultrasonic nondestructive testing, in particular to a test method for measuring uniform and non-uniform restraining force of a concrete filled steel tubular column by adopting a piezoelectric film.
Background
In the process of pressing the steel pipe concrete column, the steel pipe can generate a hoop restraining effect on the core concrete, so that the strength and the ductility of the concrete are greatly improved, and therefore, the accurate measurement of the restraining effect of the steel pipe on the core concrete plays a vital role in mastering the mechanical property of the steel pipe concrete column. However, since the hoop restraining force of the steel pipe on the core concrete exists on the narrow interface between the steel pipe and the concrete, the measuring device for the common stress strain cannot be installed, and for the square steel pipe, the restraining effect on the core concrete is still in an uneven state, and the installation of a plurality of measuring devices on the same cross section is further impossible. The piezoelectric film is light in weight, thin in film, durable, capable of working passively and widely applied to medical sensors at present, but no report is found on the aspect of detection of the concrete-filled steel tube binding force.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a test method for measuring the uniform and non-uniform restraining force of a concrete filled steel tubular column by adopting a piezoelectric film.
In order to achieve the purpose, the test method for measuring the uniform and non-uniform restraining force of the concrete filled steel tubular column by adopting the piezoelectric film is characterized by comprising the following steps of: the method ignores the stress of the piezoelectric film in the plane, and simplifies the stress state into a unidirectional stress state which is only vertical to the upper and lower surfaces of the piezoelectric film and is restrained by the concrete-filled steel tube; after the piezoelectric film is polarized, electric charges are generated on the surface vertical to the polarization direction when the piezoelectric film is pressed, namely the film has a piezoelectric effect, the electric charge quantity output by the surface of the piezoelectric film is in direct proportion to the pressure vertical to the surface and the area of the piezoelectric film, the pressure of the piezoelectric film can be obtained according to the change of the electric charge quantity of an external circuit, and the constraint force of the concrete-filled steel tube column is measured; comprises the following steps:
(1) Before the core concrete was poured, the thickness was 28 μm, the dimensions 0.6cm × 0.9cm, and the effective area was 0.35cm2Dielectric constant of 110X 10-12The piezoelectric film is pasted on the inner side of the steel pipe, a hole is opened at a position 2 d-30 d away from the veneering surface to lead out a lead to output a piezoelectric signal, and d is the diameter of the hole; the purpose is to avoid the error of the constraint force measured by the piezoelectric film caused by the stress concentration of the opening position;
(2) carrying out an axis compression test on the steel pipe concrete column, and carrying out graded loading; in the initial loading stage, each stage of loading is 1/10 of the estimated ultimate load, when the steel pipe enters the yield stage, each stage of loading is 1/20 of the ultimate load, and the load holding time of each stage is 2-3 min; recording the electric signal change of the piezoelectric film after each level of load is stable;
(3) the computer analyzes and processes the changed electric signals of the piezoelectric film: according to the piezoelectric effect of the piezoelectric film, the calculation formula (1) of the positive and negative charge quantity gathered on the upper and lower electrodes of the piezoelectric film is utilized:
Q＝A·εσ (1)；
in the formula, Q is the electric charge quantity output by the surface of the piezoelectric film; a is the area of the piezoelectric film; epsilon is the dielectric constant of the piezoelectric material; sigma is the binding force to be measured; the pressure on the upper surface and the lower surface of the piezoelectric film can be obtained by measuring the change of the charge quantity of the external circuit in real time, namely the uniform and non-uniform restraining force on the concrete filled steel tubular column is detected in real time; and the computer analyzes and processes the changed electric signals of the piezoelectric film so as to measure and calculate the restraint force of the hoop.
The working principle of the invention is as follows:
according to the stress characteristic of the concrete-filled steel tube column, the invention utilizes the high sensitivity of the piezoelectric film to dynamic stress and measures the interaction force between the steel tube and the concrete through the change of electric signals between the upper electrode and the lower electrode of the film.
The invention has the following advantages and beneficial effects:
compared with the prior art, the invention has the advantages that: the device of the invention can not damage the interface characteristics of the steel pipe and the concrete, the film is thin and easy to place, the testing device is simple, the measuring operation is easy, the measuring result is visual, the sensitivity and the accuracy are high, the actual measurement of the hoop restraining force in the whole stress process can be realized, the real-time detection of the hoop restraining force in the construction or service process can be realized, and the real-time monitoring of the safety and the health of the structure can be realized.
Drawings
FIG. 1 is a schematic structural diagram of a detection device for measuring the uniform restraining force of a circular steel tube concrete column by using a piezoelectric film according to the invention;
FIG. 2 is a schematic structural diagram of a detection device for measuring the non-uniform restraining force of a square steel tube concrete column by using a piezoelectric film according to the present invention.
In the figure: 1. the concrete filled steel tubular column comprises a concrete filled steel tubular column 2, a piezoelectric film 3, a lead 4 and a computer.
Detailed Description
The following describes embodiments of the present invention with reference to the accompanying drawings. Before pouring core concrete, the piezoelectric film 2 with the thickness of only 28 microns is pasted on the inner side of the steel tube, and when the concrete-filled steel tube column 1 is loaded, uniform and non-uniform constraint pressure can be directly obtained through the change of electric signals between the upper electrode and the lower electrode of the piezoelectric film 2.
Specifically, the method comprises the following steps:
(1) for a certain steel pipe concrete column 1 with the diameter of 219mm and the length of 657mm, self-compacting concrete with the internal filling compressive strength of C40 is filled, before core concrete is poured, the thickness is only 28 mu m, the size is 0.6cm multiplied by 0.9cm, and the effective area is 0.35cm2Dielectric constant of 110X 10-12The piezoelectric film 2 is pasted on the inner side of the steel pipe, a hole is opened at a position 2 d-30 d away from the veneering surface to lead out a lead 3 to output a piezoelectric signal, and d is the diameter of the hole;
(2) and carrying out an axis compression test on the steel pipe concrete column 1, and carrying out graded loading. In the initial loading stage, each stage of loading is 1/10 of the estimated limit load, after the steel pipe enters the yield stage, each stage of loading is 1/20 of the limit load, and the load holding time of each stage is about 2-3 min. Recording the electric signal change of the piezoelectric film 2 after each level of load is stable;
(3) The computer analyzes the electrical signal that processes the change of the piezoelectric film 2: according to the piezoelectric effect of the piezoelectric film 2, the calculation formula (1) of the positive and negative charge quantity gathered on the upper and lower electrodes of the film is utilized:
Q＝A·εσ，
in the formula, Q is the electric charge quantity output by the surface of the piezoelectric film; a is the area of the piezoelectric film; epsilon is the dielectric constant of the piezoelectric material; σ is the restraining force to be measured. Taking the uniform constraint force of the round steel tube as an example, the constraint force is 0.2Nu(NuLimit load), 0.35Nu、0.6Nu、0.8Nu、1.0NuAnd unloaded to 0.85N after limit loaduThe range of the electric charge quantity output from the surface of the piezoelectric thin film 2 measured at the time is as follows: 0 to 8.5 x 10-6C, at 0.35NuThe amount of charge output from the surface of the piezoelectric film 2 is zero, i.e. the restraining force is close to 0 and is 0.6NuIncrease of time binding forceTo 3.46MPa, 0.8NuThe time constraint force reaches 6.83MPa and 0.8NuThe time constraint force reaches 9.85MPa, the result is compared with the finite element calculation result, and the change trend of the two results is completely consistent.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (1)
1. A test method for measuring uniform and non-uniform restraining force of a concrete filled steel tubular column by adopting a piezoelectric film is characterized by comprising the following steps of: the method ignores the stress of the piezoelectric film in the plane, and simplifies the stress state into a unidirectional stress state which is only vertical to the upper and lower surfaces of the piezoelectric film and is restrained by the concrete-filled steel tube; after the piezoelectric film is polarized, electric charges are generated on the surface vertical to the polarization direction when the piezoelectric film is pressed, namely the film has a piezoelectric effect, the electric charge quantity output by the surface of the piezoelectric film is in direct proportion to the pressure vertical to the surface and the area of the piezoelectric film, the pressure of the piezoelectric film can be obtained according to the change of the electric charge quantity of an external circuit, and the constraint force of the concrete-filled steel tube column is measured; comprises the following steps:
(1) before the core concrete was poured, the thickness was 28 μm, the dimensions 0.6cm × 0.9cm, and the effective area was 0.35cm2Dielectric constant of 110X 10-12The piezoelectric film is pasted on the inner side of the steel pipe, a hole is opened at a position 2 d-30 d away from the veneering surface to lead out a lead to output a piezoelectric signal, and d is the diameter of the hole; the purpose is to avoid the error of the constraint force measured by the piezoelectric film caused by the stress concentration of the opening position;
(2) carrying out an axis compression test on the steel pipe concrete column, and carrying out graded loading; in the initial loading stage, each stage of loading is 1/10 of the estimated ultimate load, when the steel pipe enters the yield stage, each stage of loading is 1/20 of the ultimate load, and the load holding time of each stage is 2-3 min; recording the electric signal change of the piezoelectric film after each level of load is stable;
(3) The computer analyzes and processes the changed electric signals of the piezoelectric film: according to the piezoelectric effect of the piezoelectric film, the calculation formula (1) of the positive and negative charge quantity gathered on the upper and lower electrodes of the piezoelectric film is utilized:
Q＝A·εσ (1)；
in the formula, Q is the electric charge quantity output by the surface of the piezoelectric film; a is the area of the piezoelectric film; epsilon is the dielectric constant of the piezoelectric material; sigma is the binding force to be measured; the pressure on the upper surface and the lower surface of the piezoelectric film can be obtained by measuring the change of the charge quantity of the external circuit in real time, namely the uniform and non-uniform restraining force on the concrete filled steel tubular column is detected in real time; and the computer analyzes and processes the changed electric signals of the piezoelectric film so as to measure and calculate the restraint force of the hoop.
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| CN201910999442.4A CN110987247B (en) | 2019-10-21 | 2019-10-21 | Test method for measuring uniform and non-uniform restraining force of concrete-filled steel tubular column by adopting piezoelectric film |
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| CN201910999442.4A CN110987247B (en) | 2019-10-21 | 2019-10-21 | Test method for measuring uniform and non-uniform restraining force of concrete-filled steel tubular column by adopting piezoelectric film |
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| JP4898374B2 (en) * | 2006-06-29 | 2012-03-14 | 株式会社竹中工務店 | Strength evaluation method of steel pipe concrete column / beam joint |
| CN101936852B (en) * | 2010-07-12 | 2012-07-04 | 哈尔滨工业大学深圳研究生院 | Confirming method of axial compression bearing capacity of steel tube-FRP (Fiber Reinforced Plastic)-concrete column as well as application |
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